Fast EtherChannel

The Fast EtherChannel feature allows multiple Fast Ethernet point-to-point links to be bundled into one logical link to provide bidirectional bandwidth of up to 800 Mbps. Fast EtherChannel builds on standards based on 802.3 full-duplex Fast Ethernet to provide fault-tolerant, high-speed links between devices and servers.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see
Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Information About Fast EtherChannel

Overview of Fast EtherChannel

Cisco 7200 series routers, Cisco 7500 series routers, and Cisco 7000 series routers with the Cisco 7000 Series Route Switch Processor (RSP7000) and Cisco 7000 Series Chassis Interface (RSP7000CI).

A Cisco 7500 series router or a Cisco 7000 series router with the RSP7000 and RSP7000CI and a Catalyst 5000 switch.

Fast EtherChannel provides higher bidirectional bandwidth, redundancy, and load sharing. Up to four Fast Ethernet interfaces can be bundled in a port-channel, and the device can support up to four port channels. The Fast EtherChannel feature is capable of load balancing traffic across Fast Ethernet links. Unicast, broadcast, and multicast traffic are distributed across the links providing higher performance and redundant parallel paths. In the event of a link failure, traffic is automatically redirected to other functional links within the Fast EtherChannel.

In the Fast EtherChannel feature, IP traffic is distributed over the port-channel interface, while traffic from other routing protocols is sent over a single link. Bridged traffic is distributed on the basis of the Layer 3 information in the packet. If the Layer 3 information does not exist in the packet, the traffic is sent over the first link.

Fast EtherChannel supports all features currently supported on the Fast Ethernet interface. You must configure these features on the port-channel interface rather than on the individual Fast Ethernet interfaces. Fast EtherChannel connections are fully compatible with Cisco VLAN and routing technologies. The Inter-Switch Link (ISL) VLAN trunking protocol can carry multiple VLANs across a Fast EtherChannel. Devices attached to Fast EtherChannel links can provide full multiprotocol routing with support for host standby using the Hot Standby Router Protocol (HSRP).

The port-channel (consisting of up to four Fast Ethernet interfaces) is treated as a single interface. A port-channel is used in Cisco software to maintain compatibility with existing commands on the Catalyst 5000 switch. You can create the Fast EtherChannel by using the
interfaceport-channel interface configuration command. You can assign up to four Fast Ethernet interfaces to a port-channel by using the
channel-group interface configuration command.

Additional Fast EtherChannel features include:

Hot Standby Router Protocol (HSRP)

For more information about configuring HSRP, see the “Configuring IP Services” chapter in the
IP Application Services Configuration Guide.

Cisco Express Forwarding (formerly known as CEF) and distributed Cisco Express Forwarding (formerly known as dCEF)

For more information about configuring Cisco Express Forwarding, see the “Configuring Cisco Express Forwarding” module of the
IP Switching Configuration Guide.

How to Configure Fast EtherChannel

Configuring the Port-Channel Interface

SUMMARY STEPS

1.enable

2.configure terminal

3.interfaceport-channelchannel-number

4.ipaddressip-addressmask

5.mac-addressieee-address

6.end

7.showinterfaceport-channel

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interfaceport-channelchannel-number

Example:

Device(config)# interface port-channel 3

Creates the port-channel interface and enters interface configuration mode. The channel number ranges from 1 to 4.

Step 4

ipaddressip-addressmask

Example:

Device(config-if)# ip address 10.108.1.27 255.0.0.0

Assigns an IP address and subnet mask to the Fast EtherChannel.

If you configure Cisco Inter-Switch Link (ISL), you must assign an IP address to the subinterface (for example, interface port-channel 1.1—an IP address per VLAN) and you must specify the encapsulation with the VLAN number under that subinterface (for example, encapsulation is 100).

Step 5

mac-addressieee-address

Example:

Device(config-if)# mac-address 1111.2222.3333

(Optional) Assigns a static MAC address to the Fast EtherChannel.

If you do not assign a static MAC address on the port-channel interface, the Cisco software automatically assigns a MAC address. If you assign a static MAC address and later remove it, the Cisco software automatically assigns a MAC address.

Displays information about the port-channel interface so that you can verify the configuration.

What to Do Next

Note

If you want to use the Cisco Discovery Protocol (formerly known as CDP), you must configure it on the physical Ethernet, Fast Ethernet, or Gigabit Ethernet interface and not on the port-channel interface.

Caution

Fast EtherChannel supports Cisco Express Forwarding and distributed Cisco Express Forwarding, depending on your release. We recommend that you clear all explicit
iproute-cachedistributed commands from Fast Ethernet interfaces before enabling distributed Cisco Express Forwarding on the port-channel interface to give the port-channel interface proper control of its physical Fast Ethernet links. When you enable Cisco Express Forwarding or distributed Cisco Express Forwarding globally, all interfaces that support Cisco Express Forwarding or distributed Cisco Express Forwarding are enabled. When Cisco Express Forwarding or distributed Cisco Express Forwarding is enabled on the port-channel interface, it is automatically enabled on each of the Fast Ethernet interfaces in the channel group. However, if you have previously disabled Cisco Express Forwarding or distributed Cisco Express Forwarding on the Fast Ethernet interface, Cisco Express Forwarding or distributed Cisco Express Forwarding is not automatically enabled. In this case, you must enable Cisco Express Forwarding or distributed Cisco Express Forwarding on the Fast Ethernet interface.

Disables the IP address if the Fast Ethernet interface already exists and has an IP address assigned.

Step 5

channel-groupchannel-number

Example:

Device(config-if)# channel-group 3

Assigns Fast Ethernet interfaces to the Fast EtherChannel. The channel number is the same as the channel number that you specified when you created the port-channel interface.

Step 6

exit

Example:

Device(config-if)# exit

Exits interface configuration mode and returns to global configuration mode. Repeat Steps 1 through 4 to add up to four Fast Ethernet interfaces to the Fast EtherChannel.

Step 7

end

Example:

Device(config)# end

Exits global configuration mode and returns to privileged EXEC mode.

Step 8

showinterfacesport-channel

Example:

Device# show interfaces port-channel

Displays information about the Fast Ethernet interface so that you can verify the configuration.

Removing Fast Ethernet Interfaces from a Fast EtherChannel

Caution

The port-channel interface is a routed interface. Do not enable Layer 3 addresses on the physical Fast Ethernet interfaces. Do not assign bridge groups on physical Fast Ethernet interfaces because bridges may create loops. Also, you must disable the spanning tree protocol.

Displays information about the Fast Ethernet interface so that you can verify the configuration.

What to Do Next

The Cisco software automatically removes a Fast Ethernet interface from the Fast EtherChannel if the interface goes down, and the software automatically adds the Fast Ethernet interface to the Fast EtherChannel when the interface comes up.

Fast EtherChannel relies on keepalives to detect whether the line protocol is up or down. Keepalives are enabled by default on Fast Ethernet interfaces. If the line protocol on the interface goes down because of not receiving a keepalive signal, the Fast EtherChannel detects that the line protocol is down and removes the interface from the Fast EtherChannel. However, if the line protocol remains up because keepalives are disabled on the Fast Ethernet interface, the Fast EtherChannel cannot detect this link failure and does not remove the interface from the Fast EtherChannel even if the line protocol goes down. This behavior can cause unpredictable results. The implementation of the Port Aggregation Protocol in a subsequent release of this feature will remove the dependency on keepalives.

Related Documents

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

Feature Information for Fast
EtherChannel

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Table 1 Feature Information for Fast
EtherChannel

Feature Name

Releases

Feature
Information

Fast
EtherChannel

12.1(4)E

12.2(52)SG

The Fast
EtherChannel feature allows multiple Fast Ethernet point-to-point links to be
bundled into one logical link to provide bidirectional bandwidth of up to 800
Mbps. Fast EtherChannel builds on standards based on 802.3 full-duplex Fast
Ethernet to provide fault-tolerant, high-speed links between devices and
servers.